elimination: when finding dependent load/stores, realize that
they are the same if aliasing claims must alias instead of relying
on the pointers to be exactly equal. This makes load elimination
more aggressive. For example, on 403.gcc, we had:
< 68 gvn - Number of instructions PRE'd
< 152718 gvn - Number of instructions deleted
< 49699 gvn - Number of loads deleted
< 6153 memdep - Number of dirty cached non-local responses
< 169336 memdep - Number of fully cached non-local responses
< 162428 memdep - Number of uncached non-local responses
now we have:
> 64 gvn - Number of instructions PRE'd
> 153623 gvn - Number of instructions deleted
> 49856 gvn - Number of loads deleted
> 5022 memdep - Number of dirty cached non-local responses
> 159030 memdep - Number of fully cached non-local responses
> 162443 memdep - Number of uncached non-local responses
That's an extra 157 loads deleted and extra 905 other instructions nuked.
This slows down GVN very slightly, from 3.91 to 3.96s.
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vector instead of a densemap. This shrinks the memory usage of this thing
substantially (the high water mark) as well as making operations like
scanning it faster. This speeds up memdep slightly, gvn goes from
3.9376 to 3.9118s on 403.gcc
This also splits out the statistics for the cached non-local case to
differentiate between the dirty and clean cached case. Here's the stats
for 403.gcc:
6153 memdep - Number of dirty cached non-local responses
169336 memdep - Number of fully cached non-local responses
162428 memdep - Number of uncached non-local responses
yay for caching :)
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If we see that a load depends on the allocation of its memory with no
intervening stores, we now return a 'None' depedency instead of "Normal".
This tweaks GVN to do its optimization with the new result.
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former does caching, the later doesn't. This dramatically simplifies
the logic in getDependency and getDependencyFrom.
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query. This makes it crystal clear what cases can escape from MemDep that
the clients have to handle. This also gives the clients a nice simplified
interface to it that is easy to poke at.
This patch also makes DepResultTy and MemoryDependenceAnalysis::DepType
private, yay.
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of a pointer/int pair instead of a manually bitmangled pointer.
This forces clients to think a little more about checking the
appropriate pieces and will be useful for internal
implementation improvements later.
I'm not particularly happy with this. After going through this
I don't think that the clients of memdep should be exposed to
the internal type at all. I'll fix this in a subsequent commit.
This has no functionality change.
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pointer bitcasts and GEP's", and centralize the
logic in Value::getUnderlyingObject. The
difference with stripPointerCasts is that
stripPointerCasts only strips GEPs if all
indices are zero, while getUnderlyingObject
strips GEPs no matter what the indices are.
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This speeds up a particular testcase from 12+ hours to 5 seconds with little perceptible loss of quality.
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GVN expects that all inputs which to an instruction fall somewhere in the value
hierarchy, which isn't true for these.
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bug as well as a missed optimization. We weren't properly checking for local
dependencies before moving on to non-local ones when doing non-local read-only
call CSE.
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in both time and memory savings for GVN. For example, one testcase went from 10.5s to 6s with
this patch.
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Specifically, introduction of XXX::Create methods
for Users that have a potentially variable number of
Uses.
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when something changes, instead of moving forward. This allows us to
simplify memset lowering, inserting the memset at the end of the range of
stuff we're touching instead of at the start.
This, in turn, allows us to make use of the addressing instructions already
used in the function instead of inserting our own. For example, we now
codegen:
%tmp41 = getelementptr [8 x i8]* %ref_idx, i32 0, i32 0 ; <i8*> [#uses=2]
call void @llvm.memset.i64( i8* %tmp41, i8 -1, i64 8, i32 1 )
instead of:
%tmp20 = getelementptr [8 x i8]* %ref_idx, i32 0, i32 7 ; <i8*> [#uses=1]
%ptroffset = getelementptr i8* %tmp20, i64 -7 ; <i8*> [#uses=1]
call void @llvm.memset.i64( i8* %ptroffset, i8 -1, i64 8, i32 1 )
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memsets that initialize "structs of arrays" and other store sequences
that are not sequential. This is still only enabled if you pass
-form-memset-from-stores. The flag is not heavily tested and I haven't
analyzed the perf regressions when -form-memset-from-stores is passed
either, but this causes no make check regressions.
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This fires dozens of times across spec and multisource, but I don't know
if it actually speeds stuff up. Hopefully the testers will show something
nice :)
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safer (when the passed pointer might be invalid). Thanks to Duncan and Chris for the idea behind this,
and extra thanks to Duncan for helping me work out the trap-safety.
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not safe. This is fixed by more aggressively checking that the return slot is
not used elsewhere in the function.
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another sret function, it should pass its own sret parameter to the tail callee, allowing it to fill in the correct
return value. llvm-gcc does not emit this by default. Instead, it allocates space in the caller for the sret of
the tail call and then uses memcpy to copy the result into the caller's sret parameter. This optimization detects
and optimizes that case.
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into alias analysis. This meant updating the API
which now has versions of the getModRefBehavior,
doesNotAccessMemory and onlyReadsMemory methods
which take a callsite parameter. These should be
used unless the callsite is not known, since in
general they can do a better job than the versions
that take a function. Also, users should no longer
call the version of getModRefBehavior that takes
both a function and a callsite. To reduce the
chance of misuse it is now protected.
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